1. Field of the Invention
The present invention relates generally to magnetic shields for read heads of magnetic sensors, and more particularly to a flux closure layer that reduces sensor noise from edge flux leakage of magnetic shields.
2. Description of the Prior Art
As is well known to those skilled in the art, the fabrication of magnetic heads having read head elements and write head elements involves the deposition and shaping of a plurality of thin film layers of various materials utilizing photolithographic, etching and other process steps. The read head elements and write head elements are fabricated on the surface of a substrate base, and after fabrication, the substrate is sliced in such a manner as to create the magnetic heads. In typical prior art tape head fabrication processes, read head elements and write head elements may be fabricated adjacent to or on top of each other and aligned so as to create a linear sensor element of a tape drive head when the fabrication process is complete, or the read head elements and write head elements may be fabricated one on top of the other to form a magnetic head of a hard disk drive. The focus of the present invention is upon the fabrication and composition of the magnetic shield structure of the read head element.
Regarding the magnetic shield layer, it is known in the prior art that where the layer is composed of a homogenous material such as permalloy, that it will have superior magnetic shielding properties; however this material is quite ductile and metal bridging problems are known to occur during head polishing and also with wear from usage, that can result in electrical shorting by the permalloy across an insulation layer to the sensor elements of the magnetic head. It is likewise known in the prior art that where the magnetic shield layer is composed of a harder, less ductile layer, bridging and electrical shorting are not a problem. However, such a shield may be less magnetically stable than a permalloy shield, and additionally, such a shield may be susceptible to corrosion and degraded performance where a permalloy shield is not. A prior art shield that resolves some of these problems involves the fabrication of a laminated shield, in which alternating thin film layers of nitrided permalloy and Fe are sequentially deposited. A specific laminated, nitrided shield layer of the prior art includes an Fe(N) 600 Å, NiFe(N) 200 Å laminated layer, in which this two sublayer lamination is repeated a plurality of times to create the shield layer. A problem with such a laminated magnetic shield is that magnetic flux can leak from the edges of the laminations of the magnetic shield. This edge flux can flow to the MR sensor element and cause unwanted signal noise, thus degrading the performance of the magnetic head. As is described below, the present invention involves an improvement in the magnetic shield structure in which a flux closure layer is deposited next to the laminated magnetic shield. The flux closure layer serves to prevent the edge flux from the laminated magnetic shield from flowing to the MR element, thereby reducing the signal noise present in the prior art laminated magnetic shield design.